The present invention relates to an apparatus for treating various types of particulate material in various ways, specifically pulverizing, mixing, granulating, coating and otherwise treating such materials. This apparatus comprises a casing defining a treating chamber having a discharge opening for permitting overflows of the material under treatment, drive means for rotating the casing at high speed to produce a centrifugal force for pressing the material in the casing against an inside wall surface of the casing, treating members diposed in the casing to be rotatable relative to the inside wall surface of the casing, a classifier communicating with the discharge opening.
A known treating apparatus having a construction as noted above, taking a pulverizing or crushing apparatus for example, is disclosed in U.S. Pat. No. 4,529,135 (or Japanese patent application laid open under No. 58-153544).
According to the known construction, however, the treating chamber defined by the rotatable casing is open substantially over an entire top area thereof, and this opening provides an overflow outlet for the material under treatment. Therefore, it is possible for a considerable amount of material not sufficiently treated, namely coarse particles not reduced to fine particles, to leave the treating chamber as entrained in gas flows along with fine particles. Since coarse particles naturally require a much higher conveying gas speed than fine particles, a great amount of gas must be supplied from a gas supply unit which raises the power cost for supplying the gas. Furthermore, the classifier receiving the material from the treating chamber must undergo a heavy workload, and its classifying precision tends to be poor because of a wide distribution of particle sizes. Thus, the known construction has room for improvement.
Moreover, the crusher and the classifier in the known construction are separate entities, wherein the discharge outlet of the crusher is connected to the inlet of the classifier by a pipe, and the coarse particle outlet of the classifier is connected to the inlet of the crusher by another pipe. This constitutes the further disadvantage of the prior art that the entire installation tends to be large. The course particles returning from the classifier are no longer very coarse since they have undergone at least one cycle of treatment. Since such particles are mixed with fresh untreated material for feeding to the crushing chamber, the crushing efficiency is somewhat poor with respect to the coarse particles returning from the classifier. The known construction remains to be improved in this respect also.
A known treating apparatus for mixing, granulating and drying particulate materials is disclosed in Japanese patent publication No. 59-43216. A known treating apparatus for coating particulate materials is disclosed in Japanese patent publication No. 61-8735.
Demands for treating apparatus of this type are expected to grow at an increasing rate in the fields of medicines, foods, cosmetics, and new materials such as ceramics. However, conventional treating apparatus including those disclosed in the foregoing publications are not satisfactory.